Valve gated nozzle having a valve pin with a sensor

ABSTRACT

An injection molding apparatus includes a manifold for delivering a melt stream of moldable material to a nozzle melt channel of a nozzle. A valve pin extends through the nozzle melt channel and is axially movable to selectively open a gate to allow communication with a mold cavity. A sensor is coupled to a forward end of the valve pin. The sensor may be a pressure sensor and/or temperature sensor in direct contact with the melt stream to provide pressure and/or temperature information to a controller.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.10/809,707, filed Mar. 26, 2004, now U.S. Pat. No. 7,182,893, which is acontinuation-in-part of U.S. application Ser. No. 10/268,885 filed Oct.11, 2002, now U.S. Pat. No. 6,739,863 B2, issued May 25, 2004 whichclaims the benefit of U.S. Appl. No. 60/328,404, filed Oct. 12, 2001,abandoned. Each of these applications is incorporated by referenceherein in its entirety.

FIELD OF THE INVENTION

The present invention relates generally to an injection moldingapparatus having at least one nozzle with a valve pin.

BACKGROUND OF THE INVENTION

In an injection molding apparatus, the molding conditions of each of aplurality of mold cavities must be as close as possible to predeterminedideal molding conditions in order to ensure that high quality moldedparts are produced. Any significant variation in the temperature and/orpressure of one or more mold cavities may result in the production ofsub-standard molded parts.

Pressure and/or temperature sensors are used in injection moldingapparatus to determine molding conditions of each of a plurality of moldcavities. It is known to position a pressure and/or temperature sensoralong a nozzle melt channel, a manifold melt channel, and/or within amold cavity to measure a processing condition at that respectivelocation of the injection molding apparatus. In a valve gated injectionmolding system, it is known to position a pressure measurement deviceupstream of a valve pin such that it will measure pressure when a rearend of the valve pin is in direct or indirect contact therewith when thevalve pin is in a retracted position.

SUMMARY OF THE INVENTION

Embodiments of the present invention are directed to an injectionmolding apparatus having at least one manifold for receiving a meltstream of moldable material and delivering the melt stream to at leastone nozzle that is in fluid communication with a mold cavity. Theinjection molding apparatus includes at least one valve pin that isaxially movable within a melt channel thereof for controlling melt flowwith respect to the mold cavity. In the present invention, at least onesensor is coupled to a forward end of the valve pin such that the sensormeasures a processing condition of the melt stream.

In another embodiment of the present invention, there is provided aninjection molding apparatus having a first melt channel for receiving afirst melt material from a first melt source and having a second meltchannel for receiving a second melt material from a second melt source.A valve pin extends through the first melt channel of the nozzle and isaxially movable for controlling the flow of the first and second meltmaterials, wherein the valve pin includes a sensor for detecting atleast one processing condition of the first and/or second melt materialscoupled thereto. A mold cavity is in fluid communication with the nozzlevia a respective mold gate and the valve pin has an end portion forselectively opening and closing the mold gate.

BRIEF DESCRIPTION OF THE FIGURES

Embodiments of the present invention will now be described more fullywith reference to the accompanying drawings in which like referencenumerals indicate similar structure.

FIG. 1 is a side sectional view of a portion of an injection moldingapparatus according to an embodiment of the present invention, theinjection molding apparatus including a valve-gated nozzle with a valvepin in an open position.

FIG. 2 is a side sectional view similar to FIG. 1 with the valve pin ina closed position.

FIG. 3 is a side view partly in section of a valve pin according to anembodiment of the present invention.

FIGS. 4A-4B are side sectional views of a downstream portion of a valvepin according to various embodiments of the present invention.

FIG. 5 is a side sectional view of an injection molding apparatusaccording to another embodiment of the present invention.

FIG. 6 is a side sectional view of a portion of an injection moldingapparatus according to another embodiment of the present invention, theinjection molding apparatus including a valve-gated nozzle with a valvepin in an open position.

FIG. 7 is a side sectional view of a portion of a multigate injectionmolding apparatus according to another embodiment of the presentinvention.

FIGS. 8A, 8B and 8C are side sectional views of a portion of aco-injection molding apparatus according to another embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to FIGS. 1 and 2, an injection molding apparatus 10 isgenerally shown. The injection molding apparatus 10 includes a manifold12, a plurality of nozzles 14 and a mold cavity block 16. The manifold12 includes an inlet 18 for receiving a melt stream of moldable materialfrom a machine nozzle (not shown). The melt stream flows from the inlet18, through an inlet channel 20 and plurality of intermediate meltchannels 22 to a plurality of outgoing melt channels 24, which arelocated downstream of the intermediate melt channels 22. The manifoldblock 12 is heated by a heater 26, which may be any suitable type ofmanifold heater known in the art.

The nozzles 14 are positioned downstream of the outgoing melt channels24 of the manifold 12. Each nozzle 14 includes a nozzle body 28 having anozzle melt channel 30 extending there through. The nozzle melt channel30 receives melt from the outgoing melt channel 24 of the manifold 12.The nozzle 14 is heated by a nozzle heater 32, which may be mounted tothe nozzle 14 in any way known in the art. For example, nozzle heater 32may surround the exterior of the nozzle body 28, as shown in FIG. 1, oralternatively, nozzle heater 32 may be embedded within the nozzle body28.

The nozzle melt channel 30 ends at a gate 34, which is the entrance fromthe nozzle melt channel 30 into a mold cavity 36 in the mold cavityblock 16. Melt passes from the nozzle melt channel 30 past gate 34 andinto mold cavity 36. Mold cavity block 16 is cooled by a coolant, whichflows through cooling channels 37.

A valve pin 11 is located within each nozzle melt channels 30 to controlthe flow of melt into a respective mold cavity 36. Each valve pin 11reciprocates within the nozzle melt channel 30 to selectively open andclose the gate 34.

The valve pin 11 is actuated by an actuator 38. Actuator 38 may be anysuitable type of actuator. For example, actuator 38 may include achamber 40, having a first fluid passage 42 proximate one end of thechamber 40, a second fluid passage 44 proximate the opposing end of thechamber 40, a piston 46 in the chamber 40 and an arm 48 extending fromthe piston 46 to outside the chamber 40. The arm 48 may connect thepiston 46 inside the chamber 40 to the valve pin 11, using any suitableconnection means. For several reasons including ease of cleanout, thearm 48 preferably connects to the valve pin 11 outside of any meltchannels 22 and 30, so that the melt is not permitted to seep into theconnection. The arm 48 may be fixedly connected to the piston 46. Afluid, such as a hydraulic oil or air, for example, may be introducedinto the chamber 40 on one side of the piston 46 at a selected pressureand/or removed on the opposing side of the piston 46 to move the piston46, (and in turn, the arm 48 and the valve pin 11), in a directioneither towards or away from the gate 34. The movement of the valve pin11 towards and away from the gate 34 controls the melt flow into themold cavity 36.

The valve pin 11 extends through a mold plug 50 into the outgoing meltchannel 24 and nozzle melt channel 30. Mold plug 50 seals around valvepin 11 to inhibit melt from escaping from outgoing melt channel 24. Themold plug 50 acts as a bearing to permit sliding of the valve pin 11there through, so that valve pin 11 can move, as desired in meltchannels 24 and 30. In the position shown in FIG. 1, valve pin 11 is inthe open position to permit melt flow into mold cavity 36.

Valve pin 11 includes a valve pin body 52, which has an end portion 53having an end surface 54. The end portion 53 of the valve pin 11 may betapered, as shown in FIGS. 1 and 2, or alternatively, may have anysuitable shape, such as cylindrical. The end portion 53 is generallyused for gating purposes, i.e. for the closing of the gate 34 and istherefore shaped to mate with the gate 34. In the position shown in FIG.2, the valve pin 11 is in the closed position, with the end portion 53being positioned in the gate 34, to prevent melt flow into mold cavity36.

Valve pin 11 further includes a head 55. The head 55 is used tofacilitate connecting the valve pin 11 to the piston 46. The head 55 ispositioned at the upstream end of the valve pin 11. The head 55 isgenerally a disc-shaped portion that has a larger diameter than that ofthe valve pin body 52. The head 55 may be captured by any suitable meansknown in the art, so that the valve pin 11 is removable from the arm 48.

A pressure sensor 56 is provided in an internal passage 60 of the valvepin 11. The pressure sensor 56 includes a connector 58, which links asensing piece 62 of the pressure sensor 56 to a controller 65 forreceiving, processing, transmitting and/or recording the measurementsfrom pressure sensor 56. The connector 58 may be a single wire ormultiple wires depending on the type of pressure sensor 56 that is used.Any suitable type of pressure sensor capable of sensing pressuresbetween 100 and 3000 bar may be used. For example, pressure measuringsensor no. 6183A, which is produced by Kistler Instrument Corp. ofAmherst, N.Y., may be suitable.

The sensing piece 62 of the pressure sensor 56 is positioned so that adownstream or melt contacting surface 63 of the sensing piece 62 isflush with the end surface 54 of the valve pin 11. This allows thepressure sensor 56 to be in direct contact with the melt stream so thatthe pressure of the melt may be obtained when the valve pin 11 is in anyposition.

The connector 58 of the pressure sensor 56 exits the valve pin body 52at an exit point 64, which is outside of the nozzle melt channel 30 andmanifold outgoing melt channel 24. Exit point 64 may be at any suitableposition on valve pin 11, such as, for example, on the side of the valvepin body 52, as shown. The position of exit point 64 should be such thatthe connector 58 does not interfere with the movement of valve pin 11 inmelt channels 24 and 30. The connector 58 should be long enough betweenthe valve pin 11 and the controller 65, so that it does not interferewith the movement of the valve pin 11.

The pressure sensor 56 allows for continuous measurement of the meltstream. When the valve pin 11 is in the retracted position of FIG. 1,the pressure sensor 56 measures the pressure of the melt in the nozzlemelt channel 30. When the valve pin 11 is in the extended position ofFIG. 2, in which the end portion 53 of the valve pin 11 engages the gate34, the pressure sensor measures the pressure of the melt in the moldcavity 36.

Each valve pin 11 in the injection molding apparatus 10 is equipped withpressure sensor 56 so that the pressure in each of the plurality ofnozzle melt channels 30 and respective mold cavities 36 may be measuredand compared with other nozzle melt channels 30 and mold cavities 36 inthe injection molding apparatus 10.

In one embodiment, the controller 65 may operate to provide feedback toadjust the amount of packing performed by the valve pin 11 followinginjection. The controller 65 would direct the valve pin 11 to pack moreor less depending on the pressure in the mold cavity 36. In oneembodiment, this arrangement may be used with an electrical actuator sothat packing is effectively controlled as would be apparent to one ofordinary skill in the art.

Because the pressure measured by the pressure sensor 56 is an indicationof the viscosity of the melt, the controller 65 may further beconfigured to communicate with the nozzle heater 32 in order to adjustthe temperature of the melt in the nozzle melt channel 30. Adjusting themelt temperature changes the melt viscosity and therefore may be used toset the pressure to a desired pressure.

Referring to FIG. 3, another embodiment of the present invention isshown. In this embodiment, a valve pin 11 a includes a sensing piece 62a of a pressure sensor 56 a that is located downstream of an end ofvalve pin 11 a and is external thereto. A suitable material is used tofill any air gap between the sensing piece 62 and the valve pin 11 a, sothat the valve pin 11 a maintains a smooth outer surface.

Referring to FIG. 4A, another embodiment of a valve pin 11 b is shown.Valve pin 11 b is similar to valve pin 11 of FIGS. 1 and 2; however, inaddition to pressure sensor 56 b, valve pin 11 b includes a thermocouple66. The thermocouple 66 extends through an internal passage 60 b and iscoupled to a controller (not shown) in a similar manner as the pressuresensor 56 b. Conductive fill 68 is provided around the pressure sensor56 b and the thermocouple 66 to be a continuous surface with nozzle endsurface 54 b. Thermocouple 66 may be any suitable type of thermocouplecapable of sensing temperatures in the range of at least 100° C. to 400°C.

FIG. 4B, shows another embodiment of a valve pin 11 c. Valve pin 11 c issimilar to valve pin 11 b of FIG. 4A; however, sensing piece 62 c of thepressure sensor 56 c fills the entire downstream end of internal passage60 c. As such, thermocouple 66 c is spaced from an end surface 54 c ofthe valve pin 11 c and extends only to an upstream end of the sensingpiece 62 c.

Reference is made to FIG. 5, which shows an injection molding apparatus10 h in which valve pin 11 h is used with a nozzle 514. Valve pin 11 his similar to valve pin 11 of FIGS. 1 and 2, however, an end portion 53h does not taper towards end surface 54 h. Nozzle 514 is similar tonozzle 14, except that nozzle 514 includes a nozzle body 528 with anoffset nozzle melt channel 530. Valve pin 11 h passes through manifold12, through nozzle body 528 and into nozzle melt channel 530. Valve pin11 h is actuated by actuator 38 h to open and close a valve gate 34 h.

Reference is made to FIG. 6, which shows another embodiment of aninjection molding apparatus 10 i. This embodiment includes a nozzle 614,which is similar to nozzle 14, except that nozzle 614 includes a body628 having a thermocouple 154 coupled thereto. Thermocouple 154 may beused to measure the temperature of some portion of the nozzle 614. Forexample, the thermocouple 154 may be used to measure the temperature ofthe nozzle body 628 or the temperature of the nozzle heater 32.

Reference is made to FIG. 7, which shows a multi-gate injection moldingapparatus 700. Molding apparatus 700 includes a mold cavity plate 702with a plurality of mold cavities 704. Each mold cavity 704 includes aplurality of gates 734 permitting entry of melt into mold cavity 736from a plurality of points. Molding apparatus 700 further includesmanifold 712, and a plurality of nozzles 714, whereby more than onenozzle 714 may feed melt to a single mold cavity 736. Valve pins 11 jmay be included in molding apparatus 700, to provide melt pressureinformation from each nozzle 714 leading to a mold cavity 736.

FIG. 7 discloses another embodiment of the current invention in whichpressure sensor 56 is embedded in a movable valve pin 11 j that controlsthe flow of the molten material through melt channel 722 of manifold712. FIG. 7 shows two nozzles 714 feeding a single mold cavity 736 viatwo separate mold gates 734 in a simultaneous, sequential or dynamicfeed injection molding manner. These methods require that the flow ofmolten material into the mold cavity be controlled through valve pins 11j located in the manifold melt channel in order to control the locationof any knit lines that may occur in the mold cavity when two or morestreams of melt delivered by separate nozzles 714 meet.

Unlike previous known designs where additional holes are bored into amanifold to place a pressure sensor in contact with a pressurized melt,the embodiment of FIG. 7 illustrates an apparatus wherein no additionalmanufacturing steps are required on the manifold to enable pressuresensor 56 to be located in direct contact with the melt flowing throughmanifold melt channel 722. This is achieved by embedding or attachingpressure sensor 56 to the movable valve pin 11 j. As such, the necessityof additional holes being needed in the manifold for pressure sensors iseliminated, holes which can be vulnerable to melt leakage and which arealso difficult to manufacture.

In addition to the foregoing advantage, the embodiment of FIG. 7provides a movable pressure sensor that allows the measurement of themelt pressure in the manifold at various positions along the meltchannel. In another embodiment related to FIG. 7, an additionaltemperature sensor (not shown) may be attached to valve pin 11 j tomeasure the temperature of the melt flowing through the manifold meltchannel. This temperature sensor may be a thermocouple or any otherknown temperature measuring device. Such an arrangement allows for thesimultaneous measurement of the pressure and temperature of the meltflowing through the manifold melt channel at more than one location. Inone embodiment, the pressure and the temperature sensors are connectedto a controller (not shown) that uses this information to providepositioning data to each actuator that moves valve pins 11 j in themanifold channel. These actuators can be fluidly, mechanically orelectrically driven.

FIG. 7 also illustrates pressure and temperature sensors, i.e., pressuresensor 753 and thermocouple 754, located adjacent to the mold cavity tomeasure these parameters in the cavity.

Reference is made to FIGS. 8A, 8B and 8C, which show a co-injectionmolding apparatus 800 with a co-injection nozzle 814. Valve pin 811,that is similar to valve pin 11 in FIGS. 1 and 2, is incorporated intothe co-injection apparatus 800. Co-injection is the injection ofdifferent materials into a single mold cavity 836 to form, for example,a product having several layers. Some of the layers may be made from thesame material, and some layers may be made from a different material.Some layers may flow into the mold cavity 836 simultaneously, while somelayers may flow into the mold cavity 836 sequentially. Co-injection isused for many applications, such as preforms for soft drink bottles.

Molding apparatus 800 may include a plurality of manifolds, such asmanifolds 804 and 806. Manifolds 804 and 806 receive melt from aplurality of melt sources (not shown), and may have a plurality of meltchannels therein, which are shown at 808, 810 and 812. Each melt channel808, 810 and 812 carries melt which forms a different layer of the finalmolded product.

Co-injection nozzle 814 includes a first nozzle melt channel 815, asecond nozzle melt channel 816 and a third nozzle melt channel 818,which receive melt from manifold melt channels 808, 810 and 812respectively. Such a configuration is described in WIPO Publ. No. WO00/54954 (Gellert et al.) incorporated by reference in its entiretyherein. Nozzle melt channel 815 is typically central along its length,while melt channel 816 is typically annular and may join with meltchannel 815, so that a second layer of material may be introduced intomelt channel 815. Melt channel 818 may also be annular and join meltchannel 815 to introduce a third layer of material to melt channel 815.

In another embodiment of the present invention, the pressure sensor isembedded in an outer surface of the valve pin 11 instead of extendingthrough an internal passage thereof. The pressure sensor is embedded ina manner that ensures that the outer surface of the valve pin remainssmooth.

The actuator 38 has been described as being a hydraulic piston-type, andas a rack-and-pinion type. It will be appreciated by persons skilled inthe art that alternatively, the actuator 38 may be an electric rotaryactuator, or an electric linear actuator, which can be connected to thevalve pin 11.

The many features and advantages of the invention are apparent from thedetailed specification and, thus, it is intended by the appended claimsto cover all such features and advantages of the invention that fallwithin the true spirit and scope of the invention. Further, sincenumerous modifications and changes will readily occur to those skilledin the art, it is not desired to limit the invention to the exactconstruction and operation illustrated and described, and accordinglyall suitable modifications and equivalents may be resorted to, fallingwithin the scope of the invention.

1. An injection molding apparatus comprising: a manifold including afirst manifold melt channel for delivering a first melt material and asecond manifold melt channel for delivering a second melt material; aninjection molding nozzle having a first melt channel for receiving thefirst melt material from the first manifold melt channel and having asecond melt channel for receiving the second melt material from thesecond manifold melt channel; a valve pin having a valve pin body with asegment that slidably extends through the first melt channel of thenozzle, the valve pin being axially movable for controlling the flow ofthe first and second melt materials; a processing sensor coupled to andpositioned at least partially within the segment of the valve pin bodythat extends within the first melt channel; and a mold cavity in fluidcommunication with the nozzle via a respective mold gate, wherein thevalve pin has a downstream end portion for selectively opening andclosing the mold gate.
 2. The injection molding apparatus of claim 1,wherein at a first axial position of the valve pin the processing sensormeasures a pressure of the first melt material.
 3. The injection moldingapparatus of claim 2, wherein at a second axial position of the valvepin the processing sensor measures a pressure of the second meltmaterial.
 4. The injection molding apparatus of claim 1, wherein whenthe end portion of the valve pin is seated within the mold gate in theclosed position the processing sensor measures a pressure of the meltmaterial in the mold cavity.
 5. The injection molding apparatus of claim1, wherein said processing sensor is a thermocouple.
 6. The injectionmolding apparatus of claim 5, wherein the thermocouple is positionedwithin the end portion of the valve pin.
 7. The injection moldingapparatus of claim 5, further comprising: at least one thermocouplecoupled to the nozzle.
 8. The injection molding apparatus of claim 1,wherein said processing sensor is a pressure sensor.
 9. The injectionmolding apparatus of claim 1, further comprising: a controller forcommunicating with the processing sensor.
 10. The injection moldingapparatus of claim 1, wherein the processing sensor has a meltcontacting surface that is flush with an end surface of the valve pin.11. The injection molding apparatus of claim 1, wherein the processingsensor has a melt contacting surface that is downstream of an endsurface of the valve pin.
 12. The injection molding apparatus of claim1, wherein the processing sensor includes a pressure sensor and atemperature sensor.
 13. The injection molding apparatus of claim 1,wherein the manifold is comprised of a first manifold including thefirst manifold melt channel and a second manifold including the secondmanifold melt channel.
 14. An injection molding apparatus comprising: aninjection molding nozzle having a first melt channel for receiving afirst melt material from a first melt source and having a second meltchannel for receiving a second melt material from a second melt source;a valve pin having a body segment that slidably extends within the firstmelt channel of the nozzle, the body segment including a downstream endportion of the valve pin being axially movable for controlling the flowof the first and second melt materials; a pressure sensor coupled to anddisposed at least partially within the body segment of the valve pin;and a mold cavity in fluid communication with the nozzle via arespective mold gate, wherein the valve pin end portion is selectivelypositionable for opening and closing the mold gate.
 15. The injectionmolding apparatus of claim 14, wherein at a first axial position of thevalve pin within the first melt channel the pressure sensor measures apressure of the first melt material.
 16. The injection molding apparatusof claim 15, wherein at a second axial position of the valve pin withinthe first melt channel the pressure sensor measures a pressure of thesecond melt material.
 17. The injection molding apparatus of claim 14,wherein when the end portion of the valve pin is seated within the moldgate in the closed position the pressure sensor measures a pressure ofthe melt material in the mold cavity.
 18. The injection moldingapparatus of claim 14, further comprising: at least one thermocouplecoupled to the valve pin and axially movable therewith.
 19. Theinjection molding apparatus of claim 18, further comprising: at leastone thermocouple coupled to the nozzle.
 20. The injection moldingapparatus of claim 14, further comprising: at least one thermocouplecoupled to the nozzle.
 21. The injection molding apparatus of claim 14,further comprising: a controller for communicating with the pressuresensor.
 22. The injection molding apparatus of claim 14, wherein thesecond melt channel is annular and is radially displaced from the firstmelt channel.
 23. The injection molding apparatus of claim 14, whereinthe pressure sensor is at least partially embedded within the endportion of the valve pin.
 24. The injection molding apparatus of claim14, wherein the pressure sensor is embedded within the end portion ofthe valve pin such that a melt contacting surface of the pressure senoris flush with a downstream end surface of the valve pin.
 25. Theinjection molding apparatus of claim 8, wherein the pressure sensor ispositioned within the end portion of the valve pin.